There are several individual anti-fall protective devices sliding on a support, such as a rope, orientated vertically and fixed at its upper portion.
These devices are connected by a head rope to an operator when they are intended to protect the latter from falling.
To this effect, these devices have been designed so as to slide upwards and downwards along the support and able to lock on the latter should the operator fall.
Some of the models of these devices are complicated and tighten an element on the support under the dynamic effect caused by a fall of the operator connected to the device.
The most advanced models do have the drawback of comprising a large number of fragile elements. Most of these devices mean that constant vigilance is required to ensure they are clean as they are sensitive to the presence of debris and dust which adversely affect their operational efficiency.
The U.S. Pat. No. 4,923,037 describes an automatic anti-fall stoppage device able to move along a vertical support. This device includes a mounted toothed wheel for rotating inside its housing joined to the inside of an external housing and is elastically stressed in a direction applying the toothed wheel against the support passing into a vertical channel fitted at the front portion of the external housing. When the device moves along the support, the toothed wheel is rotary-driven via its friction on the latter. If the fall speed of the device along the support reaches a predetermined value, the corresponding speed of rotation of the toothed wheel triggers a centrifugal clutch mechanism which stops rotation of the toothed wheel. The friction between the support and the stopped toothed wheel then causes the housing to pivot in a direction ensuring the tightening of the support between the toothed wheel and the external housing and locking of the device on the support.
In this device, where the toothed wheel is used both to detect the moving speed of the device and as a tightening element, the centrifugal clutch system, which triggers automatic tightening, is a costly and fragile element sensitive to dust.
The French patent published under the N.sup.o 2574511 also concerns a device for automatically tightening on a safety rope. This device includes a roller able to move along a ramp between a lower rest position, in which it is distanced from the safety rope, and an upper position where it tightens the rope so as to lock the device on the latter. A lever, hooked to the head rope connected to the user, engages the mobile roller under the dynamic effect of a fall of the user so as to bring it to a position enabling it to be tightened.
Owing to the lightness of the tightening roller able to rise along the guiding ramp under the effect of jerks or vibrations, this device is extremely sensitive to poorly controlled functioning and is likely to function erratically.